Ktor usage cleanup

[whyoleg]

Modifications:

• drop unused dependencies after migration to kotlinx-io
• drop old client websocket tests and different engines
  • with ktor 3.1 CIO will be supported for all targets and so it will be enough to test the logic with it on all targets
• extract websocket tests to separate modules

[github-actions]

Test Results

  862 files   -  16    862 suites   - 16   32m 15s ⏱️ - 6m 58s
3 777 tests  -  96  3 062 ✅  -  72    715 💤  - 24  0 ❌ ±0 
7 944 runs   - 384  6 418 ✅  - 288  1 526 💤  - 96  0 ❌ ±0 

Results for commit 06539d0. ± Comparison against base commit aeaf294.

♻️ This comment has been updated with latest results.